The invention relates to an elevator in which, for the purpose of suspending and driving an elevator car, flat belts are used as suspension means. The invention relates to the problem of guiding flat belts on belt-sheaves, i.e. on traction and deflection sheaves of an elevator installation.
From U.S. Pat. No. 6,401,871 a suspension means for an elevator is known that has the form of a flat belt with rectangular cross section, and whose belt body consists of an elastic material and several embedded tensile cords parallel to its longitudinal axis. For the purpose of guiding the flat belt on the belt-sheaves used as traction or deflection sheaves, two different means are proposed. According to a first proposal, the belt running surfaces of the flat belt, as well as the running surfaces of the sheave, are provided with complementary contours. These contours ensure guidance of the flat belt on the belt-sheave. According to a second proposal, the flat belts are guided by disk-shaped guide elements that project beyond the sheave running surfaces at the edge of a belt-sheave or between several sheave running surfaces.
The methods proposed in U.S. Pat. No. 6,401,871 for guiding the flat belts have significant disadvantages.
As described in U.S. Pat. No. 6,401,871, in the first proposal of a belt guide with contoured running surfaces the tractive capacity between a traction sheave and the flat belt is also increased. This solution has the disadvantage that as a result of the increased tractive capacity, there is a safety risk that in a situation in which the elevator car or the counterweight rests on its lower travel limits, the tractive capacity between the traction sheave and the flat belt remains so high that the elevator car or the counterweight can be caused to move further in upward direction.
Guidance of the flat belt by means of disk-shaped guide elements has also proved disadvantageous. If the edge of the flat belt is pressed with a certain contact pressure against these guide elements that rotate with the belt-sheave, the flat belt is laterally raised by the latter in such manner that the side surface of the belt climbs radially on the guide element and can provide practically no further resistance against movement of the flat belt. Consequently, flat belts can fall off the belt-sheave or be prematurely destroyed.